Communication systems are facing a wide variety of system integrity challenges in today's ever advancing electronic world. The rapidly increasing use of wireless communication systems, often co-located with complementary wireless systems provides increased opportunity for signal corruption between intended users. Additionally, in some instances denial of signal reception to unwanted users is highly desirable both in civilian and military settings. In order to accomplish the above goals a mixture of techniques have arisen to ensure accurate signal reception only to desired users.
Among the more prominent transmission schemes for communication systems are systems that implement spread spectrum, frequency hopping and correction code techniques or hybrid systems. Such schemes allow for minimizing the effects of signal interference such as, crosstalk or noise, or alternatively, the effects of intentional signal jamming. In addition it is often desirable to transmit signals in any given region without altering those individuals not intended to receive the transmission.
One example of a system utilizing such technologies is the Joint Tactical Information Distribution System ("JDIDS"). JDIDS is a spread spectrum, time-division-multiple-access system that allows a very large number of designated users to communicate among themselves. A specific waveform having a specified number of pulses with each pulse having a specified number of date bits, has been developed to support JDIDS communications. Additionally, receiver architecture is somewhat standardized generally categorized by total functionality and the physical size of the unit
JTIDS users forming a specific network each have a common code sequence that determines the pseudo-noise and frequency-hopping modulation. A JTIDS network is considered "nodsness", and the loss of any one user does not result in a degradation of transmitted information by or to other users. Furthermore, users may transit or receive information to all other users on a given network, thereby forming a virtual information "bus", with respect to the defined network. Thus, the network routinely consists of JTIDS terminals located upon platform that are moving at very high speeds in the case of certain jet aircraft or missile applications, as well as stationary units or unit based upon ships or hand-held.
Prior art methods of processing JTIDS signals was to utilize correlators of various configuration, keyed upon certain data bits in a waveform pulse subsequent to analyzing predetermined data bit positions for the transmitted message. In this manner JTIDS network users were able to synchronize transmitted signals and utilize transmitted information.
To counter the effects of interference, intentional or otherwise, on a given frequency some users resort to utilizing high power transmitters. This brute force type approach can be exceedingly expensive in terms of allocated resources, especially in light of hopped signals and sophisticated interference practices. An alternate approach involves the use of a filter, in continuous operation, to counter the effects of a known interfering signal of relatively narrow bandwidth. This type of interference is typically referred to as excitable interference and is accordingly relatively easy to remove from the desired signal.
A more difficult type of interference to contend with that which varies in duration and frequency, or closely resembles the desired signal, often referred to as non-excises interference. Not only is the identification of such non-excitable interference more complex than existing interference, but the removal, suppression and adaptation to varying parameters is also of increased sophistication.
Accordingly, a new method of processing communication systems signals of a given format that readily identifies non-excitable interference and suppresses or removes such interference is highly desired.